I'm running two 4850s on a 16x / 4x PCIe 2.0 board. I've run 3Dmark Vantage a bunch of times, and there isn't any noticeable performance difference with my setup than the benchmarks posted on the web in reviews, at 16x / 16x or 8x / 8x. I'd probably need to repeat the mark a whole bunch of times to get a good sampling size, but if there is a negative effect, I can say with confidence that it is very small.

I would imagine (though not certain) that a 4x PCIe 1.x would be a bit more noticeable bottleneck, however.

I'm running two 4850s on a 16x / 4x PCIe 2.0 board. I've run 3Dmark Vantage a bunch of times, and there isn't any noticeable performance difference with my setup than the benchmarks posted on the web in reviews, at 16x / 16x or 8x / 8x. I'd probably need to repeat the mark a whole bunch of times to get a good sampling size, but if there is a negative effect, I can say with confidence that it is very small.

I would imagine (though not certain) that a 4x PCIe 1.x would be a bit more noticeable bottleneck, however.

Thats good to read, eventho you are using another videocard as well another mainboard.. but good to read once again that performance on 16x / 4x is still really good.

Allright, i decided to go for a 5850 instead of Crossfire 5770, something some of you suggested before. I thought it wouldnt be possible to return my 5770, but it is possible.
Now one last thing, the guy from the store told me they only have a MSI 5850 in stock, would this be a good choice for a 5850? i dont find that much about the MSI on the net compared with ASUS or Sapphire.